Tracy Porter isn't afraid to guess. The Broncos' new cornerback — arguably the team's top offseason acquisition not named Peyton Manning — was guessing along with Ben Roethlisberger all night.

"At times you do (guess)," Porter said. "What happens at the corner position is you see it happening but you don't believe what you see, and that gives them that little window to fit it in."

Porter was busy all night. He had five tackles a few minutes into the second quarter. He nearly had Big Ben picked off early in the fourth quarter. In one of the most underrated plays of the game, Porter was near the goal line in the second quarter when he leapt, reached and defelected away a Roethlisberger pass intended for a wide-open Heath Miller in the back of the end zone.

"They ran a switch route where they picked the linebacker," Porter said. "I saw it out of the corner of me eye and did my best to get a hand on the ball."

Porter would get his score late in the game to seal the win. Porter stepped in front of Emmanuel Sanders, who was running a sideline route at the Steeler 43, and returned it for a touchdown.

"I had the safety (covering) over the top, and I was going to be aggressive on anything underneath," Porter said. "They ran the wheel route, and he tried to fit it in there."

Keep the pressure on. The Broncos defense closed in a flurry with three of their five sacks on Steelers quarterback Ben Roethlisberger coming on the last four Steelers' plays of the game.

Von Miller had both of his sacks in the game during the binge, with linebacker Wesley Woodyard getting the third.

"They kind of got into it as we went," said Broncos coach John Fox. "They finished pretty strong."

Up until that final Steelers possession, Roethlisberger had been fairly effective keeping plays alive and keeping himself out of the Broncos' grasp.

Broncos cornerback Tracy Porter completes his long run into the end zone late in the fourth quarter Sunday night on a 43-yard interception return of Steelers quarterback Ben Roethlisberger's pass. (John Leyba, The Denver Post)

Rookie Derek Wolfe did get his first career sack in the first quarter as he dragged Roethlisbrger down for a 9-yard loss. And in the process, he became the sixth Broncos rookie to have a sack in his first regular-season game in franchise history. Wolfe joined Michael Brooks, Greg Kragen, Karl Mecklenburg, Willie Oshodin and Monsanto Pope.

Moore regrets hit. Safety Rahim Moore was flagged for a personal foul in the third quarter when officials said he hit Sanders helmet-to-helmet.

Moore appeared to be aiming lower, but with the speed of the play and Sanders' body position, the players wound up knocking heads.

"It was a dumb situation on my behalf," Moore said.

Photos: Broncos

Moore, who was fined $20,000 for an illegal hit last year, said he hoped he won't get fined again.

Brooking's debut. Veteran linebacker Keith Brooking didn't play a snap for the Broncos in the preseason because of a hamstring injury. On Sunday night, he made his debut on both defense and special teams.

The Broncos used Brooking in a rotation with starting weakside linebacker Woodyard, with Brooking playing mostly in base packages against the run and Woodyard playing on passing downs.

Other rookies sit. Three of the Broncos' seven draft picks were inactive for Sunday's game. Third-round running back Ronnie Hillman, fourth-round guard Philip Blake and fifth-round defensive end Malik Jackson did not dress. A fourth draft pick, second-round quarterback Brock Osweiler, did not play as Manning's backup.

Footnotes. Earlier Sunday, New England quarterback Tom Brady passed John Elway on the career touchdown passes list. Brady threw No. 301 and 302 against the Titans. ... The crowd of 76,823 was the team's fourth-largest in team history, behind three games in the 2007 season. The largest home crowd was 77,160 on Oct. 29, 2007, against the Packers.

Missy Franklin, Jenny Simpson, Adeline Gray and three other Colorado women could be big players at the 2016 Rio OlympicsWhen people ask Missy Franklin for her thoughts about the Summer Olympics that will begin a year from Wednesday in Rio de Janeiro, she hangs a warning label on her answer.